JPH0770411A - Epoxide cast articles for sulfur hexafluoride insulator - Google Patents

Abstract

PURPOSE:To provide an epoxy casting for a sulfur hexafluoide insulated devices having reduced dielectric constant and increased mechanical strength. CONSTITUTION:In epoxy resin cast articles composition from an epoxy resin composition containing a filler which increases the resistance to the decomposition products from sulfur hexafluoride, an inorganic compound having a lower dielectric constant than that of alumina and the surfaces treated is used as the filler.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a sulfur hexafluoride gas (hereinafter referred to as. "SF ₆ gas") epoxy for SF ₆ gas insulated apparatus coexists with SF ₆ gas while being used in electrical appliances filled with Notes It concerns molds.

[0002]

2. Description of the Related Art SF ₆ gas has excellent electrical insulation and arc extinguishing properties, is chemically stable, and can reduce the size and weight of equipment. Therefore, SF ₆ gas can be used as a circuit breaker, a disconnector, a transformer, or a cable. Widely used to insulate terminal bushings, electrical equipment such as busbars. This SF ₆ gas is decomposed by an arc or corona discharge generated in the equipment to generate a highly reactive decomposed product. For this reason, in the epoxy cast product used for electric equipment, it is necessary to maintain stable characteristics over many years without being eroded by the decomposition product or being deteriorated. Regarding the durability of the epoxy cast product against insulation gas decomposition products, the characteristics of the filler, which is one of the main components of the epoxy cast product, are greatly related, and normally, the filling is performed for the purpose of maintaining durability. Aluminum oxide (alumina) is often used as the agent.

[0003]

By the way, recently, in order to increase the voltage and size of electric equipment, there is a demand for an epoxy cast product which can withstand more severe conditions than before. In particular, if the epoxy resin composition used has a high relative permittivity, local electric field concentration may occur depending on the insulation design of the electrical equipment or the shape of the epoxy cast product, and the desired dielectric breakdown characteristics may not be satisfied. There are things that can not be said. The reason why the relative dielectric constant of the epoxy resin composition becomes a relatively large value is that the epoxy resin composition contains about 70% by weight of alumina.

Therefore, as a filler having a relative dielectric constant smaller than that of alumina and resistant to insulating gas decomposition products,
Aluminum fluoride, magnesium fluoride, calcium fluoride, hydrated alumina, magnesium hydroxide, calcium carbonate, calcium sulfate and the like are mentioned. But,
The cured epoxy resin containing these fillers has a problem of poor mechanical strength.

The present invention has been made in view of these circumstances, and an object thereof is to provide an epoxy cast product for SF ₆ gas insulation equipment having a low dielectric constant and excellent mechanical strength. .

[0006]

In order to achieve the above-mentioned object, the present invention provides an epoxy cast product comprising an epoxy resin composition containing a filler for improving the resistance of SF ₆ gas to decomposition products. The filler is an inorganic compound which has a lower relative dielectric constant than alumina and is surface-treated. It is preferable to use colloidal alumina or aluminum alkoxide liquid as the surface treatment liquid of the inorganic compound.

The epoxy resin composition used in the present invention is obtained by adding a filler to an epoxy resin base comprising an epoxy resin, an acid anhydride type curing agent, and, if necessary, a curing accelerator. After degassing the composition under reduced pressure,
It is poured into a mold and cured by heating to obtain an epoxy cast product.

The epoxy resin is preferably one having two or more epoxy groups in the molecule, such as a bisphenol epoxy resin, a cycloaliphatic epoxy resin, a glycidyl ester type epoxy resin, a cresol novolac type epoxy resin, and a phenol novolac type epoxy resin. Examples include resins.

Examples of acid anhydride type curing agents include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylendomethylenetetrahydrophthalic anhydride. It is also possible to use two or more of these in combination.

Examples of the curing accelerator include benzyldimethylamine, tridimethylaminomethylphenol, 2-ethyl-4-methylimidazole and the like.

The filler must be an inorganic compound having a relative dielectric constant lower than that of alumina and being surface-treated, and examples of the inorganic compound include hydrated alumina, magnesium hydroxide,
Examples thereof include calcium carbonate, calcium sulfate, aluminum fluoride, magnesium fluoride, and calcium fluoride, and two or more kinds of these may be used in combination. Also,
Alumina which has been conventionally used can also be used together if necessary.

For the surface treatment of the filler (inorganic compound), colloidal alumina (alumina sol) or aluminum alkoxide liquid is preferably used. In the case of alumina sol, the alumina sol and the filler are mixed and then dried. Thus, the surface treatment of the filler can be performed. In the case of an aluminum alkoxide liquid, the surface treatment of the filler can be performed by mixing the aluminum alkoxide liquid and the filler, hydrolyzing the mixture, and then drying the mixture. By using these surface treatment liquids, conventionally used silane coupling agents,
An epoxy resin cured product having improved mechanical strength and crack resistance as compared with surface treatment with a titanate coupling agent, a fatty acid metal salt, etc. was obtained. It is presumed that a thin film of alumina was formed on the surface of the filler by the surface treatment using the alumina sol or the aluminum alkoxide liquid, and this film contributed to the improvement of the properties of the cured epoxy resin product. This is because that.

Alumina sol is a colloidal solution of hydrated alumina having water as a dispersion medium, and a commercial product having an alumina content of 10 to 20% is used as it is or diluted with water, alcohol or the like. Alumina sol has particle size (feather-like, rod-granular), particle size (10mμ × 100mμ, 10-20m)
μ), crystalline form (amorphous, boehmite), stabilizer (C
l ⁻ , CH ₃ COO ⁻ , NO ₃ ⁻ ), which can be used in the present invention, but low viscosity products containing 10 to 20 mμ of boehmite-based rods to granular colloidal particles are preferable. is there.

Aluminum alkoxide liquids include aluminum triisopropylate, aluminum trisecondary butyrate, etc., and those that are solid at room temperature are n
-The solution is dissolved in a solvent such as hexane, and the liquid product at room temperature is used as it is or as a solution diluted with the solvent.

When the above-mentioned filler and the surface treatment liquid are mixed, it is preferable to appropriately set the concentration of the liquid (aluminum content) and the ratio of the filler powder. When setting, calculate so that the alumina content of the filler finally added by surface treatment is in the range of 0.5 to 30% by weight. When the alumina content of the filler added by the surface treatment is less than 0.5% by weight, the curing of the treatment becomes insufficient, and when it exceeds 30% by weight, the relative dielectric constant of the filler becomes large, and economically. It is disadvantageous because it is disadvantageous.

The concentration of the surface treatment liquid and the mixing ratio of the filler powder and the surface treatment liquid are optimum in consideration of the above-mentioned conditions, the ease of wetting of the powder at the time of mixing the two, and the fluidity suitable for the drying work process. Select the conditions. When drying the filler in the surface treatment, it is necessary to select a drying method and conditions in which the alumina fine particles in the treatment liquid contribute to the coating formation on the filler surface efficiently, and a uniform filler slurry wet with the surface treatment liquid is selected. It is desirable to dry the powder with a spray dryer. The main part of the spray dryer comprises a sprayer for spraying the slurry, an air heater, a spray drying chamber, a device for collecting and separating dry particles, and an exhaust fan, and the hot air and the spray are brought into contact with each other in countercurrent or cocurrent. Hot air temperature is 150 to 550 ℃
The drying time is about 5 to 20 seconds. In the spray dryer, there is an advantage that by appropriately setting the conditions, aggregation can be suppressed and the slurry can be dried without significantly changing the particle size distribution before treatment. The powder dried by the spray dryer may be mixed with the surface treatment solution again and repeatedly treated. The powder dried by the spray dryer may be further heat-treated in a high temperature furnace if necessary. Upon drying the slurry treated with the aluminum alkoxide solution, steam is introduced into hot air to perform hydrolysis and drying at the same time, or the slurry is previously hydrolyzed in a warm and high-humidity atmosphere and then dried.

In order to improve the mechanical strength and crack resistance, the amount of the filler added in the present invention is 150 parts including 100 parts by weight of the epoxy resin base, including the compounding amount of alumina when alumina is used in combination. It is preferable to select from the range of up to 350 parts by weight in consideration of characteristics such as casting workability.
Since aluminum conductors and electrodes are usually embedded in the epoxy cast product of the present invention, crack resistance is unsatisfactory when the amount of the filler added is less than 150 parts by weight including the amount of alumina compounded when alumina is used in combination. If it is more than 350 parts by weight, it becomes difficult to satisfy the casting workability.

Therefore, by using an inorganic compound whose relative dielectric constant is lower than that of alumina and which has been surface-treated as a filler for improving the resistance to decomposition products of SF ₆ gas, the surface of the inorganic compound is an epoxy resin cured product. Since it is modified so as to contribute to the improvement of mechanical properties, it is possible to obtain an epoxy cast product having a low dielectric constant and excellent mechanical strength, which is suitable for SF ₆ gas insulation equipment.

[0019]

EXAMPLES Examples of the present invention will be described below.

Various components were blended according to the blending composition shown in each column of Examples 1 to 7 and Comparative Examples 1 to 7 in Table 1.

The seven types of filler surface-treated products used in Examples 1 to 7 were subjected to the following treatments.

Six kinds of fillers before surface treatment (hydrated alumina,
Magnesium hydroxide, calcium carbonate, calcium sulfate, calcium fluoride, aluminum fluoride) has an average particle diameter of 15 to 20 μm and a cumulative weight percentage of particles of 45 μm or less of 90.
% Magnesium is used. Magnesium fluoride has an average particle size of 5 μm and cumulative weight% of particles of 45 μm or less.
Used 100%.

As the surface treatment liquid, colloidal alumina liquid [trade name Alumina sol-520 (manufactured by Nissan Chemical Industries, Ltd., dispersion medium: water, alumina content: 20% by weight) is used as it is without dilution] and aluminum An n-hexane solution (ASB concentration 75% by weight) of tri-secondary butyrate [abbreviation ASB manufactured by Koriyama Kasei Co., Ltd.] was used.

With respect to the four kinds of fillers of hydrated alumina, magnesium hydroxide, calcium carbonate and calcium sulfate, 1000 parts by weight of the filler and 300 parts by weight of the colloidal alumina solution are stirred and mixed to form a uniform slurry, which is then sprayed. Using a drying device, make this a dry powder, and
Heat treated for hours. Each of these was mixed with the epoxy resin base as a surface-treated product, degassed under reduced pressure, and injected into the mold.
A test piece was prepared by heat curing at 30 ° C. for 40 hours.

Calcium fluoride, aluminum fluoride,
For the three types of fillers of magnesium fluoride,
1,000 parts by weight and 450 parts by weight of n-hexane solution of ASB are mixed by stirring to form a uniform slurry, which is then placed in an atmosphere of 80 ° C and 100% relative humidity for 4 hours for hydrolysis, and surface treatment is performed as described above. Each was mixed with an epoxy resin base as a product to prepare a test piece.

In Comparative Examples 1 to 7, untreated fillers were used, and test pieces were prepared in the same manner as in the above Examples.

The test pieces prepared as described above were evaluated for relative dielectric constant, bending strength and crack resistance, and the results are shown in the lower column of Table 1. Each evaluation method is as follows.

The relative permittivity and bending strength were tested according to JIS K6911.

Regarding the crack resistance, a heat cycle test shown in Table 2 was carried out on an epoxy resin curing test piece having a diameter of 25 mm and a length of 60 mm, in which a bolt having a length of 50 mm was embedded. An ethanol bath cooled by a refrigerator was used on the low temperature side, and an air constant temperature bath was used on the high temperature side.

[0030]

[Table 1]

[0031]

[Table 2]

As is clear from Table 1, the test pieces of Examples 1 to 7 (epoxy cast products) according to the present invention all have a small relative dielectric constant and improved bending strength and crack resistance. . On the other hand, Comparative Example 2 in which the filler is only alumina has a large relative dielectric constant, and Comparative Examples 1 and 3 to 7 in which the untreated filler is used are inferior in bending strength and crack resistance.

It should be noted, epoxy castings resistant SF ₆ discharge decomposition gas of the Examples 1-7 of Table 1 are both good, S
It was useful for F ₆ gas insulation equipment.

[0034]

In summary, according to the present invention, an epoxy cast product having a low dielectric constant and excellent mechanical strength suitable for SF ₆ gas insulation equipment can be obtained.

Claims (2)

[Claims] 1. An epoxy cast product comprising an epoxy resin composition containing a filler for improving resistance to decomposition products of sulfur hexafluoride gas, wherein the filler has a lower dielectric constant than alumina and a surface. An epoxy cast product for sulfur hexafluoride gas insulation equipment, which is a treated inorganic compound. 2. An epoxy cast product for sulfur hexafluoride gas insulation equipment, characterized in that colloidal alumina or aluminum alkoxide liquid is used as a liquid for surface-treating the inorganic compound.